1. Field of the Invention
The present invention relates to an oscillating circuit, and particularly relates to an oscillating frequency drift detecting method and circuit.
2. Description of the Prior Art
FIG. 1 is a schematic diagram illustrating the relation between temperature and an output oscillating frequency of the crystal oscillator. The oscillating frequency output by the crystal oscillator may drift under different temperatures. The drift will cause a curve in an S shape, thereby the curve is called a S curve. Such oscillating frequency drift will cause obvious effect to an electronic apparatus. One of the compensating methods is utilizing a temperature compensated crystal oscillator to solve this issue. The temperature compensated crystal oscillator costs a much higher price than a normal one, however. Another method is acquiring the S curve in advance (ex. provided by the manufacturer), and utilizing another crystal oscillator to compensate it. However, such compensation operation needs complicated control, even the S curve is acquired.